The resistor and voltmeter were connected in parallel and connected to an ideal voltage source.

| June 25, 2021 | education

The resistor and voltmeter were connected in parallel and connected to an ideal voltage source. The voltmeter showed a voltage of 10 V. Then the resistor and voltmeter were connected in series and connected to the same source. This time the reading of the voltmeter was 6 V. Find the ratio of the resistances of the resistor and the voltmeter.

RU is the resistance of the voltmeter.

R1 is the resistance of the resistor.

Ohm’s law:

U = I * R.

1) 6V dropped on the voltmeter, we get the ratio:

6 = I * RU.

Let’s calculate the current in the voltmeter:

I = RU / 6.

2) Source voltage – 10V. This voltage is applied across the voltmeter and resistor.

This means that the resistor dropped 10 – 6 = 4V. Let’s calculate the current in the resistor:

4 = I * R1.

I = R1 / 4.

3) When connected in series, the current in all sections of the circuit is the same. Let’s equate the currents:

RU / 6 = R1 / 4.

RU = (6 * R1) / 4.

RU = 1.5 * R1.

The resistance of the voltmeter is 1.5 times greater.



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